Fig. 2. Formation of MCSs in fibrin hydrogels with varying stiffness.

(A) An individual B16-F1 cell grows into an MCS in fibrin gel with stiffness of 90 Pa within 4 days. (B) MCSs formed after 5-day culture from an individual B16-F1 cell in fibrin hydrogels with stiffness of 90 Pa (left), 420 Pa (middle), and 1050 Pa (right). Scale bars, 50 μm (A and B). (C) Variation in the MCS number with cell culture time in the fibrin hydrogels. (D) Increase in MCS size plotted as a function of culture time, plotted for hydrogels with different stiffness. The stiffness of 3D fibrin gels with concentrations of 1, 4, and 8 mg ml⁻¹ is 90, 420, and 1050 Pa, respectively. Figures were reproduced with permission from Liu et al. (15) (A to D).